Large Volumes Of Aqueous Solutions Research Articles

Adsorption performance of Pb(II) ions on green synthesized GO and rGO: Isotherm and thermodynamic studies

Graphene oxide (GO) and reduced graphene oxide (rGO) are efficient and low-cost adsorbent carbon-based materials for removing Pb(II) ions from wastewater. In this article, the adsorption performance of environmentally friendly graphene oxide and reduced graphene oxide, which shows high adsorption capacity for Pb(II) ions, has been compared for the first time to our knowledge. Besides, the various characterization techniques are used such as X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy and described in detail as well. In addition, adsorption isotherms and thermodynamic studies are discussed to comprehend the adsorption process as well. From the adsorption isotherms, the maximum adsorption capacities of Pb(II) ions on GO and rGO calculated from the Langmuir (117.6 mg/g) and Dubinin–Radushkevich isotherms (138.5 mg/g), respectively, higher than reported studies in the literature. By thermodynamic investigation, it was found that the adsorption of Pb(II) ions on GO and rGO was spontaneous and exothermic. This study will be established as a basis for future studies and will be especially valuable in understanding the potential of graphene-based materials, which are rising stars that can be considered as promising and effective adsorbents in the removal of heavy metal ions from large volumes of aqueous solutions.

Trichotomic separation of light and heavy lanthanides and Am by batchwise multi-stage extractions using TODGA

To achieve trichotomic separation of light lanthanides (Ln), heavy Ln, and Am, batchwise multi-stage extractions using N,N,N′,N′-tetraoctyl-diglycolamide (TODGA) extractant from organic acids are studied. This technique has the advantages of both solvent extraction and chromatography, which enable successive separation and management of large volumes of aqueous solutions. Malonic acid (M-Acid) is used as the main component of the aqueous phase. It is clear that the separation factor for Nd/Am from M-Acid and that for La/Am from M-Acid + HNO3 are both around 30, thus we plan to conduct these separations.

Actinide ion uptake from acidic radioactive feeds using an extraction chromatographic resin containing a branched dialkyl amide

A dialkyl amide with branched alkyl group, viz. N,N-di(2-ethylhexyl)-propionamide (D2EHPrA) was used as the organic extractant in an extraction chromatographic resin prepared for the first time and evaluated for the separation of uranium from acidic feeds. The distribution coefficient measurements, carried out at varying HNO3 concentrations, indicated an increase in the UO22+ ion sorption with increasing nitric acid concentration. The UO22+ ion sorption kinetics and sorption isotherms with this resin were investigated in details. The column studies indicated that 8.3 mg of uranium could be loaded on a 2.1 cm3 column bed volume containing 0.35 g resin. Batch distribution data for other actinides such as Np4+ and Pu4+ indicated that the resin can also be used for effective separation of these metal ions from acidic feeds. Though the resin showed effectiveness for Np and Pu, detailed investigations dealing with macro concentrations of metal ions (in gm quantities) were restricted to uranium only due to hazardous nature of plutonium and limited availability of neptunium. The encouraging results reported in this work is an indication of the possible application of this resin for the recovery or pre-concentration of UO22+, Np4+ and Pu4+ ions from large volumes of aqueous solutions of moderate acidity.

Examination of Photocatalyzed Chlorophenols for Sequential Photocatalytic-Biological Treatment Optimization

Given the known adverse effect of chlorophenols for the aquatic environments which they can reach, the development of efficient methods both technically and economically to remove them has gained increasing attention over time. The combination of photocatalytic oxidation with biological treatment can lead to high removal efficiencies of chlorophenols, while reducing the costs associated with the need to treat large volumes of aqueous solutions. Therefore, the present paper had as its main objective the identification of the minimum photocatalytic oxidation period during which the aqueous solutions of 4-chlorophenol and 2,4-dichlorophenol can be considered as readily biodegradable. Thus, the results of photocatalytic oxidation and biodegradability tests showed that, regardless of the concentration of chlorophenol and its type, the working solutions become readily biodegradable after up to 120 min of irradiation in ultraviolet light. At this irradiation time, the maximum organic content of the aqueous solution is less than 40%, and the biochemical oxygen demand and chemical oxygen demand (BOD/COD) ratio is much higher than 0.4. The maximum specific heterotrophic growth rate of activated sludge has an average value of 4.221 d−1 for 4-chlorophenol, and 3.126 d−1 for 2,4-dichlorophenol. This irradiation period represents at most half of the total irradiation period necessary for the complete mineralization of the working solutions. The results obtained were correlated with the intermediates identified during the photocatalytic oxidation. It seems that, working solutions initially containing 4-chlorophenol can more easily form readily biodegradable intermediates.

Sorption of Pb2+, Cu2+ and Zn2+ from Aqueous Solution Using a Blended Membrane of Immobilized Karkashi (Sesame Leaves) and Sodium Alginate

Sorption techniques are widely used to remove heavy metal ions from large volume of aqueous solutions, this plays a vital role in controlling environmental pollution. Herein, the sorption of Pb2+, Cu2+ and Zn2+ with blended membrane of sodium alginate (Na-Alg) and immobilized karkashi leaves (IKAL) from aqueous solution was investigated at optimum conditions for effectiveness. Sorption capacities of the membrane for Pb2+, Cu2+ and Zn2+ were found to be 86.80, 40.60 and 39.55% respectively. The sorption behavior with respect to initial pH, ionic strength, temperature, contact time and initial metal ion concentration was investigated for optimum sorption conditions. Maximum sorption was found to occur at pH 3.0 for all the metal ions studied. Results showed that metallic ion uptake by the blended membrane declined with increase in ionic strength. This trend was also observed at an increased temperature of 50ºC for Pb2+, Cu2+ and 40ºC for Zn2+. Increase in initial metal ion concentration led to increase in metal ion uptake.
 At the end of the chemical remediation, the blended membrane was found to be effective to some extent, with the reaction being exothermic.

Magnetite nanoparticles with aminomethylenephosphonic groups: synthesis, characterization and uptake of europium(III) ions from aqueous media.

Two adsorbents with covalently bound aminomethylenephosphonic acid functions (and referred to as MNPs/AMPA and MNPs/SiO2-AMPA) were synthesized from two types of amino-functionalized magnetic nanoparticles (MNPs) via Moedritzer-Irani reaction. The sorbents with anchored dopamine ligand (MNPs/dopa) or aminopropyl groups (MNPs/SiO2-NH2), and the MNPs/AMPA were characterized by X-ray diffraction, FTIR, transmission electron microscopy and vibrating sample magnetometry. Surface modification does not adversely impact the physical properties of the starting magnetite. Compared to the size of the unmodified Fe3O4 (magnetite) nanoparticles (7-12nm), the average size of functionalized nanoparticles is increased to 10-16nm. Similarly, the magnetic saturation decreased from 67.5emu g-1 to 42.0emug-1, and the surface area is increased up to 205 m2g-1 for MNPs/SiO2-AMPA. The kinetics of the adsorption of Eu(III) on the sorbent is ultra-fast, and equilibria are attained within 5-10min at room temperature. The adsorption kinetics can be described by a pseudo-second-order model. Adsorption and desorption conditions were tested with respect to the removal of Eu(III) ions from water solution. The adsorption capacities for Eu(III) at pH7.0 are 77mgg-1 and 69mgg-1 for MNPs/AMPA and MNPs/SiO2-AMPA nanoparticles, respectively. Eu(III) was quantified by ICP-MS. The limit of detection (LOD) for Eu(III) is 0.05ngL-1 (based on the 3σ criterion), with an enrichment factor of 150. The selectivity over ions such as Tb(III), Fe(III), Zn(II), Cu(II), and Ca(II) ions was studied. Under optimal condition the distribution coefficient for Eu(III) relative to these ions is near 105mLg-1. The sorbents can be easily retrieved from even large volumes of aqueous solutions by magnetic separations. The method was tested for spiked water samples (with recoveries from 96.6-102.5%) and for rock minerals. Graphical abstract A schematic showing the regeneration of magnetite nanoparticles (MNPs), core-shell (MNPs/SiO2), and the structures with covalently bonded aminomethylenephosphonic acid (AMPA) after preconcentration of Eu(III) from largewater sample volumes onto a small specimen.

Adsorption Behavior of Co(II) and Eu(III) on Polyacrylamide/Multiwalled Carbon Nanotube Composites

Multiwalled carbon nanotubes were used for the synthesis of five different polyacrylamide/ MWCNT composites. Different polymerization techniques were applied, namely, copolymerization, template polymerization of monomers on polyacrylamide, or grafting method, all induced by γ-irradiation. Fourier transform IR spectra were used for characterization. These composites were used for studying the adsorption and separation behaviors of Co(II) and Eu(III) under various experimental conditions. Radioactive isotopes 60Co and 152+154Eu were used for tracing the corresponding elements. The adsorption on the related polymers was also studied for comparison. The Kd values for the adsorption on the nanocomposites were found to be much higher than those on the corresponding polymers. Complete adsorption was achieved on some of the synthesized nanocomposites under definite conditions, suggesting the possibility of complete isolation of Co(II) and/or Eu(III) from large volumes of aqueous solutions. Separation of Co(II) and Eu(III) from each other was also found to be possible under certain conditions.

Ordered mesoporous polymer–carbon composites containing amidoxime groups for uranium removal from aqueous solutions

Ordered mesoporous polymer-carbon composites containing amidoxime groups (AO-OMC) were successfully synthesized via in-situ polymerizing 2-Butenenitrile onto the external and internal surface of ordered mesoporous carbon (CMK-3). The characterization of small-angle X-ray diffraction, N2 adsorption–desorption isotherms and TEM confirmed that the polyacrylamidoxime was only coated on the mesopore walls with a thin layer rather than occupied the whole pores. The AO-OMC containing 16.8% polyacrylamidoxime (0.2AO-OMC) showed the highest adsorption capacity for U(VI) (322.6 mg·g−1 at pH = 5.0 and T = 298.15 K), which was significantly higher than CMK-3 (43.4 mg·g−1). XPS analysis suggested that the high adsorption capacity of 0.2AO-OMC was mainly attributed to the combination of U(VI) with abundant amidoxime groups via surface complexation and electrostatic interactions. The U(VI) selectivity was above 60% in a wide pH range from 3.0 to 5.0, which has not been reported to date, and reached the highest selectivity of 72.4% at pH = 4.0. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that uranium adsorption onto 0.2AO-OMC was an endothermic and spontaneous process, and the 0.2AO-OMC exhibited excellent reusability and structural stability without any significant changes in the adsorption capacity after ten cycles. This work highlighted the simple synthesis and application of AO-OMC as an efficient material for the high elimination of U(VI) from large volumes of aqueous solutions in environmental pollution cleanup.

Removal of radionuclides by metal oxide materials and mechanism research

With the development of civil nuclear industry, “radioactive contamination” has aroused worldwide public attention increasingly. The study on the interaction of radionuclides at solid-liquid interfaces can lead to a more profound comprehension of its diffusion, migration and transformation in the natural environment, which would make the disposal and control of radioactive wastes more effectively. The metal oxide materials have shown great potential applications in the field of radionuclides’ removal, which are mainly attributed to their multiple advantages, such as the sufficiency, the low cost, the environmental friendliness and the large sorption capacity. Herein, we reviewed the application of commonly used metal oxide materials (such as iron oxides, layered double oxides, aluminum oxides and titanium dioxides) in the sorption of radionuclides from large volumes of aqueous solutions in the last five years. The sorption properties and the main interaction mechanism were investigated and discussed through batch experiments, surface complexation models, spectroscopic techniques and theoretical calculations. Moreover, the application of the metal oxide materials in environmental radioactive pollution cleanup was also discussed. Therefore, we hope that this work would be helpful to further investigation and application of metal oxide materials in environmental radionuclide pollution management.

Synthesis of Fe3O4/CD magnetic nanocomposite via low temperature plasma technique with high enrichment of Ni(II) from aqueous solution

Herein, β-cyclodextrin (β-CD) was conjugated on the surfaces of Fe3O4 particles to synthesize magnetic Fe3O4/CD nanocomposite using a novel low temperature plasma technique. The Fe3O4/CD samples were applied in the removal of radionuclides and heavy metal ions contaminations from aqueous solutions. The synthesized Fe3O4/CD nanocomposite which showed high saturation magnetization could be likely separated by using an external magnet. The adsorption performance and underlying mechanism of Fe3O4/CD nanocomposite toward nickel ions were studied using batch technique. The adsorption kinetic of nickel ions on Fe3O4/CD surfaces could be obtained within the time period of 8h. The surface conjugated CD can obviously improve adsorption performance towards Ni(II) ions. The Fe3O4/CD samples show propitious adsorption property toward Ni(II) ions from wastewater. The experimental findings showed that Fe3O4/CD nanocomposite could be used as a highly effective adsorbent for the removal of Ni(II) ions from large volumes of aqueous solution.

Polyaniline-modified 3D-flower-like molybdenum disulfide composite for efficient adsorption/photocatalytic reduction of Cr(VI)

Polyaniline (PANI) was modified onto 3D flower-like molybdenum disulfide (MoS2) to prepare a novel organic–inorganic hybrid material, PANI@MoS2. PANI@MoS2 was characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results indicate that PANI was modified onto MoS2. PANI@MoS2 was applied as an adsorbent to remove Cr(VI) from aqueous solutions, and the adsorption isotherms fit well to the Langmuir model; the maximum removal capacity of Cr(VI) by PANI@MoS2 was 526.3 and 623.2mg/g at pH 3.0 and 1.5, respectively. PANI@MoS2 exhibited an enhanced removal capacity of Cr(VI) in comparison with bare MoS2 and other adsorbents. The adsorption of Cr(VI) on PANI@MoS2 might be attributed to the complexation between the amine and imine groups on the surface of PANI@MoS2 with Cr(VI). This study implies that the hybrid material PANI@MoS2 is a potential adsorbent for Cr(VI) removal from large volumes of aqueous solutions.

Controlled synthesized natroalunite microtubes applied for cadmium(II) and phosphate co–removal

Treatment of wastewater containing several kinds of contaminants poses great challenges, because heavy metal and inorganic anion contaminants possess different fate and transport mechanisms. Individual adsorption of Cd(II)/phosphate on clay or metallic oxides has been extensively investigated, but the mutual effects of these two species in co–existing systems have received little attention. In this study, five natroalunite samples with different morphologies were synthesized by a simple hydrothermal method with appropriate volume ratio of ethylene glycol (EG) to water. The volume ratio of EG to water plays a key role in the formation of natroalunite samples, and dramatically affects their adsorption capacities. The mutual effects of Cd(II) and phosphate on their interaction with natroalunite microtubes (NMs) were investigated by varying experimental conditions, such as pH, temperature and addition sequences. The results demonstrate that highly efficient co–removal of Cd(II) and phosphate can be accomplished using NMs, and the process is strongly dependent on solution pH and temperature via the formation of ternary surface complexes. This study implies that the hydrothermally synthesized NMs can be regarded as a potential promising material for the co–removal of Cd(II) and phosphate from large volumes of aqueous solutions in pollution management.

One-step fabrication of amino functionalized magnetic graphene oxide composite for uranium(VI) removal

Amino functionalized magnetic graphene oxide composite (AMGO), a good sorbent for U(VI), was fabricated and characterized. The AMGO was applied as a magnetic sorbent for the U(VI) removal from aqueous solutions. The AMGO can be easily recovered from the solution with the magnetic separation within one minute. The kinetic data were well-described by the pseudo-second-order equation. The Langmuir model fitted the sorption isotherm data better than the Freundlich model. The maximum sorption capacity of the AMGO for U(VI) was 141.2mg/g, displaying a high efficiency for the removal of U(VI). It was found that the U(VI) sorption was accomplished mainly via chelation or ion exchange. The thermodynamic parameters illustrated that the sorption process was spontaneous and endothermic in nature. In addition, the excellent reproducibility indicate that the AMGO can be used as a potential sorbent for removal of U(VI) from large volumes of aqueous solution.

Synthesis of magnetic polyaniline/graphene oxide composites and their application in the efficient removal of Cu(II) from aqueous solutions

The magnetic polyaniline/graphene oxide (MPANI/GO) composites were synthesized by using aniline in the presence of GO. The sorption of Cu(II) on the MPANI/GO composites were studied as a function of pH, contact time, ionic strength, foreign cation and anion ions, and the results showed that Cu(II) sorption was strongly dependent on pH, and independent of ionic strength. The sorption of Cu(II) was mainly domonated by outer-sphere surface complexation at low pH, and by inner-sphere surface complexation at high pH. The thermodynamic parameters calculated from temperature-dependent sorption isotherms indicated that the sorption process was endothermic and spontaneous. The MPANI/GO composites were effective materials for the removal of Cu(II) from large volumes of aqueous solutions and could be separated by using magnetic separation method in the practical applications.

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid-phase extraction combined with dispersive liquid-liquid microextraction and high-performance liquid chromatography.

Solid-phase extraction coupled with dispersive liquid-liquid microextraction was developed as an ultra-preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion-methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid-phase extraction coupled with dispersive liquid-liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid-phase extraction coupled with dispersive liquid-liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9-6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.

RETRACTED: High sorption of U(VI) on graphene oxides studied by batch experimental and theoretical calculations

The graphene oxides (GOs) have been studied extensively in multidisciplinary areas owing to their excellent physicochemical properties. The high theoretical surface areas and large amounts of oxygen-containing functional groups at the basal planes and the edge sites ensure their high sorption capacity for heavy metal ions and radionuclides from large volumes of aqueous solutions. Herein, the GOs were applied as adsorbents to remove U(VI) from aqueous solutions at different experimental conditions, and the results showed that the sorption of U(VI) on GOs was strongly dependent on pH and was not affected by ionic strength obviously. The sorption capacity of U(VI) on GOs is calculated to be 1330 mg/g at pH 4.5 and T = 20 °C, which is much higher than any other today’s materials. The interaction mechanism of U(VI) on GOs was simulated by the computational DFT calculations, and the results evidenced that the variation in pH values led to significant changes in the circumstance of functional groups on GOs. As the pH value increased, the weak physical sorption/outer-sphere surface complexation between the GOs and U(VI) at low pH turned into strong chemical sorption/inner-sphere surface complexation with the negative charged –O− or –COO− groups induced by the deprotonation of the functional groups at high pH.

Highly efficient and selective adsorption of In3+ on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In3+ ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In3+ intake. The structure and properties of Zn/Al-LDH and In3+ adsorbed Zn/Al-LDH (In–Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N2-sorption/desorption, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In3+ adsorption and quite stable even after the adsorption process. The selective adsorption of In3+ on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn2+, Co2+, Ni2+, Cd2+, Pb2+, and Cu2+. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In3+ from large volumes of aqueous solutions.

Graphene oxides for simultaneous highly efficient removal of trace level radionuclides from aqueous solutions

Graphene oxides (GOs) were synthesized via modified Hummers method, and were applied as adsorbents to remove radionuclides from large volumes of aqueous solutions. The single and competitive sorption of four radionuclides (i.e., U(VI), 152+154Eu(III), 85+89Sr(II) and 134Cs(I)) on the GOs from aqueous solutions were investigated as a function of pH, ionic strength and radionuclide initial concentrations using batch technique. The results showed that the GOs had much higher sorption capacity than many other contemporary materials, for the preconcentration of radionuclides from large volumes of aqueous solutions. The sorption of radionuclides on GOs obeyed the Langmuir model, and was mainly attributed to surface complexation via the coordination of radionuclides with the oxygen-containing functional groups on GO surfaces. The competitive sorption results indicated that the selectivity sorption capacities were U(VI)>Eu(III)>Sr(II)>Cs(I). The GOs are suitable materials for the efficient removal and preconcentration of radionuclides from aqueous solutions in nuclear waste management and environmental pollution cleanup.

Application of graphene oxides for the removal of Pb(II) ions from aqueous solutions: Experimental and DFT calculation

Graphene oxides (GOs) have attracted intense multidisciplinary study because of their special physicochemical properties and their possible applications. The large amount of oxygen-containing functional groups on GO surfaces makes it possible to form strong surface complexes with metal ions. Herein, the GOs are synthesized by modified Hummers method and characterized by SEM, TEM, FTIR, XRD, XPS and Raman spectroscopy techniques in detail. The results show that large amount of oxygen-containing functional groups is generated on GO surfaces during the synthesis process. The GOs are applied as adsorbents to remove Pb(II) ions from aqueous solutions and the sorption of Pb(II) is strongly dependent on pH and the sorption of Pb(II) is mainly attributed to the formation of strong surface complexes. Comparing the sorption capacities of Pb(II) on different materials, the GOs have the highest sorption capacity among todays' materials. The results of far infrared spectroscopy analysis and the DFT calculation also indicate that the binding of Pb(II) on GOs is mainly attributed to the COOH groups rather than other functional groups. The GOs may be suitable materials for the preconcentration of heavy metal ions from large volume of aqueous solutions in the near future if GOs could be synthesized in large scale at low price.

A new bubbling extraction tower: Toward liquid–liquid solvent extraction at large aqueous‐to‐oil phase ratios

Enrichment and recovery of valuable components in industrial waste waters by traditional liquid–liquid solvent extraction is not economic due to extremely low concentrations of those targets. Large‐phase‐ratio extraction exhibits potential advantages for recovery of small quantities of target components from large volume of aqueous solutions. A novel bubbling extraction tower is proposed toward performing solvent extraction at large aqueous‐to‐oil phase ratios in this work. Organic extractants were covered onto surface of gas bubbles to form a layer of organic liquid membrane and the dispersed organic phase in tower could be small enough. The target components are extracted from aqueous feed solution onto the surface of the bubbles, and the enrichment ratios could be extremely high. We develop a feasible methodology to calculate tower height and operation phase ratios of the bubbling extraction tower, which is essential for future industrial scale‐up. Experimental results in pilot test are highly consistent with calculations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3889–3897, 2015